An unmanned vehicle, which may also be referred to as an autonomous vehicle, is a vehicle capable of travel without a physically-present human operator. An unmanned vehicle may operate in a remote-control mode, in an autonomous mode, or in a partially autonomous mode.
When an unmanned vehicle operates in a remote-control mode, a pilot or driver that is at a remote location can control the unmanned vehicle via commands that are sent to the unmanned vehicle via a wireless link. When the unmanned vehicle operates in autonomous mode, the unmanned vehicle typically moves based on pre-programmed navigation waypoints, dynamic automation systems, or a combination of these. Further, some unmanned vehicles can operate in both a remote-control mode and an autonomous mode, and in some instances may do so simultaneously. For instance, a remote pilot or driver may wish to leave navigation to an autonomous system while manually performing another task, such as operating a mechanical system for picking up objects, as an example.
When an unmanned aerial vehicle (UAV) propelled by spinning rotors is operating in the vicinity of other objects, there is a risk of damage to the UAV and/or other objects. This, UAVs may be designed so as to reduce the risk of a UAV's propeller contacting objects during operation.
Some existing UAVs include features such as shrouds, ducts, and cages, which aim to shield propellers and thus make the UAVs safer. However, cages, shrouds, and ducts can have undesirable aerodynamic characteristics. Further, these features can require additional fabrication, which can increase the time and cost of manufacturing a UAV. Additionally, the added weight of a cage, shroud, and/or duct requires additional flight power and reduces flight time.
Another existing safety feature is a “prop saver.” A prop saver typically includes a small rubber O-ring attached to the propeller. The prop saver allows displacement of the propeller by 10-20° during an object strike before ejecting the propeller. The prop saver dampens the forces imparted on the propeller and object when contact occurs. After the propeller has displaced 10-20°, the propeller is ejected from the UAV, and UAV flight is discontinued. While the dampened object strike force resulting from the prop saver reduces damage to contact between the object and propeller, a prop saver may terminate UAV flight.